Restore Laravel test workaround

I accidentally dropped this during a merge, making the Laravel
job fail.

Author: nikic

azure/community_job.yml

@@ -52,6 +52,8 @@ jobs:
         git clone https://github.com/laravel/framework.git --branch=master --depth=1
         cd framework
         php7.4 /usr/bin/composer install --no-progress
+        # Hack to disable a test that hangs on azure
+        sed -i 's/PHP_OS/"Darwin"/' tests/Filesystem/FilesystemTest.php
         export USE_ZEND_ALLOC=0
         export ASAN_OPTIONS=exitcode=139
         php vendor/bin/phpunit